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Big Sandy Dam Reservoir Enlargement

Location: Farson, Wyoming

Award: Innovative Applications

Project Team

Owner/Engineer: U.S. Bureau of Reclamation Contractor: Geo-Solutions, Inc. Slag Cement: Skyway Cement

Geo-Solutions, Inc., was subcontracted to install a cement-bentonite cutoff wall for the Big Sandy Dam Reservoir Enlargement Project to prevent seepage out of Big Sandy Reservoir in Farson, WY, USA. The project is owned by the U.S. Bureau of Reclamation. The cutoff wall was constructed using a slag cement-based self-hardening slurry and installed using the slurry trenching method of construction. The cutoff wall is 4400 ft (1340 m) long and 3 ft (1 m) wide and was installed through the earthfill dike. The wall was installed to a maximum depth of 42 ft (13 m) below ground surface. It was designed to cutoff the soil and weathered rock layers that have shown historical seepage through the embankment. The bottom of the slurry cutoff wall was keyed into unweathered bedrock, which is a natural low-permeability layer.

Slag cement was used in the self-hardening slurry to improve compressive strength and lower the permeability of the hydraulic cutoff wall. Historically, slurry for self-hardening walls was comprised of bentonite and portland cement. The use of slag cement in the slurry mixture typically lowers the permeability by an order of magnitude, and also shows much higher strength and ductility.

The use of slag cement allowed the self-hardening slurry to meet the project specification for strength and permeability, while that would not have been possible with portland cement only.

Application Type

% Slag Cement Replacement


% Portland Cement


% Portland Limestone Cement

% Other SCM (if applicable)



Water/cement ratio

7-day strengths

28-day strengths

20-100 psi


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